The prior-art processes used to preserve fruit and to treat the exterior of the fruit in preparation for ultimate consumption include a treating (storage) step in a salt solution (brine) containing sulfite enriched by various elements, especially calcium or aluminum. During the treatment which lasts 3 to 6 weeks, a state of equilibrium is established between the sugar content of the fruit and the salt solution containing the sulfite which results in a reduction of the fruit's sugar content (i.e. dextrose, levulose, sucrose or saccharose and a proportionate increase in the sugar content of the brine containing the sulfite.
Therefore, it is common that the fruit in contact with the brine has an initial sugar content of 10.degree. to 12.degree. Brix and a final content of 5.degree. to 6.degree. Brix.
The fruit is then separated from the sulfite brine which is discarded. The fruit is then subjected to a so-called "bleaching" or "whitening" operation which involves several washings in order to eliminate soluble substances from the fruit which are impregnated therein such as mineral salts, phenols etc. This whitening treatment which is carried out in pure water nevertheless has several inconveniences. One of the disadvantages is that it consumes a great deal of water as it is necessary to use up to seven times the volume of water as fruit. Furthermore this treatment contributes to the problem of water pollution because it is necessary to throw away a large part of the wash water. An additional problem is that the washing operation not only removes all of the undesirable substances in the fruit that has been removed from the salt solution containing the sulfite. The principal problem with the prior-art processes, however, is that the washing process can remove practically all of the remaining sugar content of the fruit. For example the fruit having undergone the preliminary treatment in a salt containing sulfite has a sugar content of 5.degree. to 6.degree. Brix. Upon leaving the washing operation, however, the sugar content of the fruit is practically zero. Such a loss in sugar must be compensated for by an imput of the equivalent amount of lost sugar upon preservation.